Compartment syndrome is a medical condition where the pressure inside a compartment (i.e., muscle group surrounded by inelastic fascia) rises higher than the pressure in the capillaries of the tissue. Compartment syndrome leads to limited or lost circulation to the region. Compartment syndrome usually occurs after a trauma or injury to the tissues contained within the compartment. Because the fascia does not expand, bleeding or swelling that results from the trauma or injury causes increased pressure within the compartment. Venous pathways in the compartment are then restricted from draining blood and fluid from the injured area, and the pressure within the compartment continues to rise. Continued pressure increases further restrict circulation and eventually lead to the death of the affected tissue (i.e., necrosis). Necrosis will often lead to the loss of limb, and possibly loss of life in severe cases. The most common site for compartment syndrome occurs in the lower leg; specifically, in regions adjacent to the tibia and fibula.
There are four compartments in the lower human leg: the anterior (front), lateral (side next to the fibula), deep posterior (back), and the superficial posterior (back). Any one of these four compartments can yield a compartment syndrome when bleeding or swelling occurs within the compartment. Compartment syndrome can also result from a cast that is too tight, constrictive dressings, pneumatic anti-shock garments, and closure of fascial defects. The clinical conditions that may be associated with compartment syndrome include the management of fractures, soft tissue injuries, arterial injuries, drug overdoses, limb compression situations, burns, post-ischemic swelling, constrictive dressings, aggressive fluid resuscitation, and tight casts.
FIG. 1 illustrates a human leg 100 with fractured bones of the tibia 105 and fibula 110, which can lead to one or more compartment syndromes in the muscles 115 surrounding the bones. The tibia 105 and fibula 110 usually bleed in regions proximate to the physical break regions 120. This bleeding can form a large pool of stagnant blood (i.e., a hematoma). The hematoma can start pressing upon muscles 115, which may be proximate to physical break regions 120. The pressure caused by the hematoma can restrict or stop blood flow into the muscles 115 of a compartment, which leads to compartment syndrome. Normal compartment pressures are under 20 mm Hg. Concern is raised when pressures rise above 20 to 30 mm Hg, and critical intervention is often required above 30 mm Hg.
Traditional methods for diagnosing compartment syndrome include highly invasive and challenging direct pressure-measurement procedures. A needle or trocar is used to access the compartment to conduct an intra-compartmental pressure measurement. Currently, such intra-compartmental pressure measurements are the only objective and reliable diagnostic tool. The diagnosis and treatment of compartment syndrome, however, can cause significant morbidity and increase the risk for infection. Therefore, inaccurate and elevated pressure readings are a very difficult and potentially dangerous pitfall.
Current needle-based pressure measuring methods are also undesirable because they only provide a snap-shot of data at an instant of time. In other words, the needle-based pressure measuring method only provides the medical practitioner with one data point for a particular time. Once pressure is read by the medical practitioner, he or she usually removes the needle from the patient. The data obtained from a single measurement in time gives no information concerning the pressure trend, and the direction the intra-compartmental pressure is moving. The collection of single data points over long periods of time is usually not very helpful because pressures within a compartment, as well as the patient's blood pressure, can change abruptly (e.g., within minutes). Further, the pain associated with the needle-based pressure measuring method restricts the medical practitioner from taking a pressure reading within a few minutes of a previous reading.
The diagnosis of compartment syndrome before the situation becomes critical is difficult, and a missed diagnosis or false positive diagnosis can have significant consequences for the patient. Treatment of compartment syndrome typically requires a fasciotomy, which is invasive, painful, complicated, and increases risk of infection and morbidity. Therefore, it is desirable to monitor the pressure in the compartment to properly and continuously assess when surgical intervention becomes absolutely necessary.
Furthermore, these traditional methods require the patient to remain in the treatment facility if continuous monitoring of compartment pressure is required. This increases the cost of treatment for the facility and the cost and inconvenience to the patient. Therefore, methods for accurately monitoring and tracking compartment pressure remotely, for example at a patient's home, are desirable.
For more information on compartment syndrome, and diagnostic and treatment methods, reference is made to the following U.S. patent and U.S. published applications, all of which are incorporated herein by reference in their entirety: U.S. Pat. No. 4,711,248; U.S. Pat. No. 4,817,629; U.S. Pat. No. 4,858,620; U.S. Pat. No. 6,942,634; and 2008/0208011. Further, reference is made to the following U.S. patents and/or publications, all of which are incorporated herein by reference in their entirety, and the subject matter of which may be related to the present invention: U.S. Pat. No. 6,980,852; U.S. Pat. No. 7,148,803; U.S. Pat. No. 7,256,708; U.S. Pat. No. 7,461,972; and 2006/0290496.